WO1992000247A1 - Purification d'une liqueur aqueuse - Google Patents

Purification d'une liqueur aqueuse Download PDF

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Publication number
WO1992000247A1
WO1992000247A1 PCT/GB1991/000996 GB9100996W WO9200247A1 WO 1992000247 A1 WO1992000247 A1 WO 1992000247A1 GB 9100996 W GB9100996 W GB 9100996W WO 9200247 A1 WO9200247 A1 WO 9200247A1
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Prior art keywords
suspension
polymer
coagulant
particles
process according
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PCT/GB1991/000996
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English (en)
Inventor
Geoffrey Laurence Payne
Hubert Fairchild, Jr.
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Allied Colloids Limited
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Application filed by Allied Colloids Limited filed Critical Allied Colloids Limited
Priority to CA002076011A priority Critical patent/CA2076011C/fr
Priority to DK91911284T priority patent/DK0536194T4/da
Priority to JP3510755A priority patent/JPH06502112A/ja
Priority to DE69107456T priority patent/DE69107456T3/de
Priority to EP91911284A priority patent/EP0536194B2/fr
Priority to AU79955/91A priority patent/AU654135B2/en
Publication of WO1992000247A1 publication Critical patent/WO1992000247A1/fr
Priority to NO924778A priority patent/NO924778D0/no
Priority to FI925860A priority patent/FI925860A/fi

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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/5227—Processes for facilitating the dissolution of solid flocculants in water
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/54—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using organic material
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S210/00—Liquid purification or separation
    • Y10S210/902—Materials removed
    • Y10S210/917—Color

Definitions

  • This invention relates to processes of coagulating aqueous suspensions of coagulatable material using water-soluble polymeric coagulants.
  • the aqueous suspensions can be true suspensions of suspended materialor they can be liquors containing colloidally dispersed material.
  • the suspended or dispersed material is usually solid.
  • Aqueous suspensions are usually clarified by the addition of one or more water-soluble organic polymers that are called coagulants or flocculants. These terms tend to be used rather inaccurately.
  • floculant we use the term “flocculant” to denote a high molecular weight polymer that achieves its effect (i.e. flocculation) primarily by a bridging mechanism, with the result that they are sometimes referred to as bridging flocculants.
  • coagulant to indicate a lower molecular weight, highly ionic, material that achieves its effect (i.e. coagulation) primarily by adsorbing onto the particles of the suspension and changing the surface charge on them, with little or no bridging effect between particles. As a result, the coagulants are sometimes referred to as charge neutralisation coagulants.
  • the coagulants have low molecular weight and because of this, and their high ionic content, they have low solution viscosity and dissolve easily into water. Typically, the molecular weight of coagulants is never more than around 1.5 million and it is often below 1 million, and indeed when the polymer is anionic it is usually below 0.5 million. In terms of intrinsic viscosity, IV is usually below 3dl/g and generally below 2dl/g.
  • molecular weights are the values obtained by gel permeation chromotagraphy and intrinsic viscosities are the values obtained using a suspended level viscometer at 25°C in 1 molar sodium chloride aqueous solution buffered to pH 7.0.
  • Solid forms do, of course, have the advantage that they do not necessitate the transport and packaging of large amounts of water and so can be more convenient, especially to the manufacturer, than aqueous concentrates.
  • solid coagulants only constitute a very small proportion of the total polymeric coagulant market.
  • an important coagulant is polydiallyldimethyl ammonium chloride, and large amounts of this are supplied worldwide.
  • Percol 368 and Magnafloc 368 from Allied Colloids Inc. and Allied Colloids Limited respectively and this constitutes only a small proportion of the total sales of this polymer.
  • a solid grade coagulant must, of course, be in solution form before it can function as a coagulant and, heretofore, this has necessitated the user providing dissolution make-up equipment.
  • the convenience and economy to the manufacturer of supplying a solid, without the need to package and transport water, has therefore tended to be outweighed by the user preferring to obtain what was considered to be equivalent performance but without the inconvenience of having to provide make-up equipment.
  • An entirely different situation applies to flocculant polymers since these are always much higher molecular weight and many of them tend to dissolve only very slowly
  • flocculant polymers generally have molecular weights of at least 4 million and usually at least 5 million, and frequently above 10 million.
  • Intrinsic viscosity is generally above 5dl/g and frequently above lOdl/g, especially with the anionic and non-ionic polymers.
  • flocculant polymers Because of the high molecular weights, flocculant polymers have very high solution viscosities and so it is not possible to supply handlable concentrates having adequate polymer concentrations. Accordingly, the flocculants generally hae to be supplied as powders or as dispersions in oil. The polymer then has to be dissolved into water. The rate of dissolution depends upon ionic charge and molecular weight. Some dissolution can occur with some polymers within a few minutes, but many of the polymers take at least an hour to go to full solution. Such polymers include, for instance, many of the polyacrylamides.
  • Such make-up apparatus generally has to involve a storage vessel that can hold the flocculant for at least an hour while it goes into true solution.
  • SUBSTITUTE SHEET suspended solids while the polymer is still in the form of polymeric particles having a size of below lO ⁇ m. These particles can, if left long enough, be truly soluble in water but preferably the polymer is cross linked so that they cannot dissolve fully into water.
  • the very small particle size, of below lO ⁇ m, is essential. Normally it is provided by introducing the polymer particles as a dispersion that has been made by reverse phase polymerisation but in EP-A-326382 it is provided by introducing the polymer in the form of friable aggregates that have been made by bonding the substantially dry polymer particles having a size of below lO ⁇ m with an aqueous liquid and drying the aggregates, whereby the aggregates disintegrate upon addition to water to release the individual polymer particles.
  • a further object is to obtain improved performance.
  • SUBSTITUTE SHEET The invention provides a process of coagulating an aqueous suspension of coagulatable material by using a water-soluble, low molecular weight, ionic polymeric coagulant. This results in coagulation of the coagulatable material, and the coagulated material is then separated from the suspension.
  • the process comprises providing a particulate, water soluble, ionic, polymeric coagulant that has intrinsic viscosity of 0.2 to 3dl/g and that is in the form of solid particles that have a size of at least 90% by weight above 30 ⁇ m, mixing the said solid particles into the suspension and thereby dissolving the particles in the suspension and coagulating the suspension, and subjecting the coagulated suspension to a separation process and thereby separating said coagulatable material from said liquor.
  • a low molecular weight ionic coagulant polymer preferably of diallyl dimethyl ammonium chloride
  • a suspension that is to be coagulated and dissolves rapidly in the suspension and coagulates it, and the coagulated material is separated from the suspension.
  • this separation is facilitated by adding a flocculant to the coagulated suspension, for instance by adding a conventional counterionic high molecular weight flocculant solution to the suspension.
  • the performance properties are always as good as those obtained using a polymer solution and, as indicated, they are usually very much better, and yet the invention has the further advantage that it eliminates the need for equipment for handling aqueous
  • SUBSTITUTE SHEET concentrates (e.g., pumps and in-line dilution equipment) and it avoids the equipment traditionally associated with solid grade polymers, namely the make-up equipment that is traditionally installed to allow the solid grade polymer to be put into the form of a solution prior to dosage into the suspension.
  • the process definitely has the advantage that it is possible to obtain greatly improved performance at the same time as using a solid material by a simplified process and apparatus and without a make-up or dilution stage.
  • coagulatable material is used herein to embrace both materials that are already present as suspended solids and materials that are present as a colloidal dispersion. Thus it embraces particulate solids such as pigment, clay, coal and sewage solids, and it also
  • SUBSTITUTE SHEET 8 embraces colloidally dispersed materials such as colouring matter in water and humates.
  • the process of the invention can bring more of this colloidally dispersed material out of colloidal solution as a particulate solid than when the same polymer is added as a solution.
  • Flocculation processes involving bridging flocculants can be relatively slow and indeed bridging may occur during, for instance, sedimentation after addition of a flocculant.
  • coagulation processes depend primarily upon charge effects and coagulation processes therefore tend to be very fast. For instance, coagulation often precedes the addition of a bridging flocculant, and this is generally added very soon after the coagulant.
  • the polymeric coagulant starts dissolving immediately upon contact with the suspension, because the coagulant is water soluble. Accordingly it immediately makes coagulant polymer molecules available for coagulation. It is preferred that the polymer particles do go into substantially complete solution in less than about five minutes and preferably much quicker, generally within about one minute and preferably within about thirty seconds, often within about fifteen seconds.
  • Whether or not a polymer particle has dissolved can be determined by filtration in that a screen that retains a dry or gelled polymer particle will not retain a solution of the polymer particle.
  • a convenient way of testing the solubility therefore is to select a screen that retains a known proportion, for instance substantially all, of the polymer particles when dry and then to filter the aqueous suspension into which the polymer particles have been mixed and observe the proportion of polymer particles retained on the screen.
  • the retained proportion at the end of the mixing period i.e., when they should be substantially fully dissolved
  • SUBSTITUTE SHEET Generally the polymer particles are substantially individual particles but if they are aggregates that break down into smaller particles before dissolution (for instance as in EP 326382) then the size of screen that should be used for testing whether or not dissolution has occurred should be the size that retains the individual component particles within each aggregate.
  • the optimum duration for dissolution will depend upon the particular suspension and process that is being coagulated. If the rate of dissolution is too slow, some of the polymer may remain undissolved during the period when a coagulation effect is required, for instance during passage in a flow line to a flocculation stage, and so may involve the use of more polymer than would be required if it dissolved faster.
  • the polymer is substantially fully dissolved before the suspension reaches the next treatment stage, and in particular before it reaches the next point of addition of treatment chemical, for instance bridging flocculant.
  • the polymer particles can have a size as small as 30 ⁇ m it is generally preferred for the average size to be at least lOO ⁇ m and generally at least 200 ⁇ m. If the polymer particles have an average size that is too large then this can be undesirable, for instance because it can reduce the time taken to achieve dissolution. Thus although it can be above 1mm, preferably it is below 1mm and usually below ⁇ OO ⁇ m. It is generally preferred for the polymer particles to have a size of at least 90% by weight in the range lOO ⁇ m to l,000 ⁇ m, often in the range 200 ⁇ m to 800 ⁇ m. Although it is normally preferred for polymers to have a reasonably narrow range of particle sizes, in the invention it can be advantageous to have a relatively wide spread of particle sizes so as to spread the time over which polymer dissolves.
  • the ionic coagulant polymers with which this invention is concerned are the materials that have, heretofore, usually been supplied as aqueous solutions because of their low solution viscosities, and therefore the particles will inevitably tend to start dissolving very quickly, and generally will be substantially fully dissolved within about a minute, often within about half a minute. These low solution viscosity and high dissolution rates are associated with the charge density and the molecular weight (intrinsic viscosity) of the polymer.
  • the polymer will not be an ionic coagulant but will instead tend to be a bridging flocculant and, in any event, will have a solution viscosity such that it is not commercially convenient to supply it as an aqueous concentrate.
  • the optimum intrinsic viscosity depends upon the ionic charge and the particular polymer.
  • intrinsic viscosity is generally at least about 0.2, preferably in the range of about 0.5 to 3, most preferably around 0.8 to 2.4dl/g. Expressed in terms of molecular weight, it is generally preferred for the molecular weight to be below 2 million, most preferably below 1.5 and, preferably, below 1 million, although it should generally be above 100,000 and preferably above 500,000.
  • the polymer is anionic, lower molecular weights are usually desirable, and in particular the anionic polymer should have a molecular weight below 1,000,000, most usually below 500,000. It must not be too low as otherwise it will act as a dispersant rather than a coagulant and so normally the molecular weight is above 50,000, often above 100,000.
  • intrinsic viscosity this should normally be at least 0.2dl/g and is preferably not more than about 2dl/g.
  • intrinsic viscosity is in the range about 0.5 to 2dl/g, most preferably about 0.8 to 1.5dl/g.
  • the polymer can be a low molecular weight, rapidly dissolving, highly ionic, naturally occurring polymer but
  • SUBSTITUTE SHEET generally it is a synthetic polymer formed by polymerisation of a water soluble ethylenically unsaturated monomer or blend of monomers and has a high charge density. Accordingly it is preferred for at least 50%, and generally at least 80%, of the monomers from which it is formed to have an ionic charge. Although the polymer can be amphoteric, preferably all the ionic monomers have the same charge. Although polymers in which 100% of the monomers are ionic are preferred, if non-ionic monomer is present its amount is generally below 50%, and preferably below 20% by weight.
  • any of the non-ionic, ethylenically unsaturated, water soluble monomers that are conventionally present in polymeric ionic coagulants can be used, but acrylamide is preferred. It is generally best for the polymer to be a homopoly er of ionic monomer.
  • Preferred anionic monomers are ethylenically unsaturated carboxylic or sulphonic acids (including their water soluble alkali metal or other salts) .
  • Examples are 2-acrylamido-2-methyl propane sulphonic acid, methacrylic acid and, especially, acrylic acid.
  • a suitable anionic polymer is a homopolymer of sodium aerylate.
  • Preferred cationic monomers are dialkylaminoalkyl (meth) -acrylates and -acrylamides, generally as acid addition or quaternary ammonium salts, and diallyl dialkyl ammonium halides.
  • the preferred acrylates and methacrylates are preferably di-C t . 4 alkylaminoethyl (meth) acrylates and the preferred acrylamides are di-C ⁇ alkylaminopropyl (meth) acrylamides, in particular dimethylaminoethyl (meth) acrylate and dimethylaminopropyl (meth) acrylamide (with the respective methacrylate and methacrylamide compounds being particularly preferred) as acid addition and quaternary ammonium salts.
  • the most suitable cationic monomer is diallyl dimethyl ammonium chloride.
  • a single cationic monomer is used, but if desired a copolymer may be formed, for instance from diallyl dimethyl ammonium chloride and
  • SUBSTITUTE SHEET 12 dimethylaminopropyl methacrylamide salt, generallywith the latter in a minor proportion.
  • any other known ionic coagulant polymers can be used.
  • suitable polymers are polyethylene imine and polyamines, e.g. , as made by condensation of epichlorhydrin with an amine.
  • Other polymers include aminomethylolated polyacrylamide (free base or quaternary or acid salt) , poly (2-hydroxypropyl-l-N-methylammonium chloride) , poly
  • Particularly preferred polymers for use in the invention are polymers of diallyl dimethyl ammonium chloride, generally as homopoly ers but optionally with up to 20% of other monomer, generally acrylamide, having IV of about 0.6 to 3, most preferably around 0.8 to 2.5dl/g.
  • the polymer is in the form of beads.
  • the particles of polymer are preferably substantially bead shaped, for instance as made by reverse phase suspension polymerisation.
  • Reverse phase suspension polymerisation typically comprises dispersing beads of aqueous monomer in a water immiscible liquid, generally in the presence of amphiphilic polymeric stabiliser, polymerisation within the beads, drying by azeotropic distillation and then separation of the beads from the liquid, often followed by further drying. Suitable methods and materials are well known and are described in, for instance, US 2,982,749, 4,506,062 and 4,528,321. Other solid particulate forms can be used. For instance a solution of the polymer can be drum dried or otherwise dried as a film which can then be converted into flakes. If the polymer itself has characteristics such that it is difficult to provide it in the form of solid particles that can be handled without, for instance, caking, then the particles can be formed of a mixture of a carrier (that promotes formation of particles) and the
  • SUBSTITUTE SHEET polymer For instance the polymer can be distributed throughout beads of a matrix material that will liberate the polymer rapidly upon contact with water, for instance as a result of disintegration of the matrix in water.
  • a suitable matrix material is a carbohydrate, for instance starch, or an inorganic carrier material.
  • the blend can be made as in, for instance, EP-A-188489.
  • the polymer particles consist solely of the desired polymer.
  • Suitable polymers are available in bead form from Allied Colloids Inc. and Allied Colloids Limited under the trade names Magnafloc 368, Percol 368 (cationic polydiallyldimethyl ammonium chloride) and Versicol Sll (anionic polyacrylic acid) .
  • the mixing of the particulate polymeric coagulant into the suspension is normally accompanied by some degree of agitation of the suspension, although with highly soluble particles adequate mixing may be achieved merely by adding the particles to the suspension. Generally however some degree of turbulence should be applied to the suspension to promote dissolution of the particles. The turbulence that inevitably arises during flow of a stream that is being coagulated in conventional manner can be sufficient and excessive shear (eg as provided in a homogeniser) is undesirable. Accordingly the preferred mixing consists essentially of the flow along duct means leading to the separation stage, although some initial mixing may be applied to promote uniform distribution of the polymer particles as they are scattered, flowed or injected into the flowing suspension.
  • the process may be carried out batchwise, but generally the particles are added to a flowing stream of the suspension and the suspension is caused to flow turbulently along duct means from the position at which the particles are added to the position at which the separation process is initiated.
  • this flow can be along a simple duct (optionally as a launder provided with
  • SUBSTITUTE SHEET baffles to create extra turbulence or it can be along a series of ducts, for instance including some substantially downwardly extending ducts so as to promote extra turbulence.
  • the respective polymers are added as fully dissolved aqueous solutions and it is well known that it is then undesirable to continue applying shear (i.e., to continue turbulence) for too long since this tends to result in resuspension of the originally suspended particles and reduction in performance.
  • excess shear is not so undesirable, and indeed can be positively advantageous, since fresh polymer molecules can continuously be dissolved from the polymer particles and so even if the distribution of polymer on the particles of the original suspension is damaged fresh polymer molecules are available to recoagulate the surfaces of the suspension particles. Nevertheless, it is generally desirable that the entire coagulation process, and in particular the mixing or application of shear that occurs during the process, should be relatively short and preferably mixing does not continue for significant periods after the polymer has dissolved.
  • the total time that elapses between initially adding the polymer particles and introducing the coagulated suspension to the separation process apparatus is not more than about one minute, preferably not more than about thirty seconds, and most preferably not more than about fifteen seconds, and during this time the polymer particles should have been substantially fully dissolved.
  • SUBSTITUTE SHEET it is more normal to follow the addition of a coagulant solution with the addition of a flocculant solution, and in the invention it is usually preferred to incorporate a polymeric flocculant into the suspension after the coagulant polymer has dissolved and coagulated the suspension.
  • the incorporation of the flocculant may be by conventional means, such as the addition of flocculant solution followed by brief (e.g., up to 15 seconds and often less than 5 seconds) agitation to achieve thorough mixing.
  • flocculant When flocculant is used, it is usually counterionic to the coagulant polymer that is added in particulate form.
  • the coagulant polymer is preferably cationic, and so the flocculant is preferably anionic.
  • anionic coagulant followed by anionic flocculant can be useful, e.g., on some coal washery slurries.
  • a surprising advantage of the invention is that the amount of flocculant that is required to achieve any particular level of clarification is generally less, when the coagulant polymer is added in particulate form, than when the coagulant polymer is added as a solution.
  • the amount of counterionic flocculant may be one fifth to three quarters, typically around half, of the amount normally required.
  • the flocculant may be any of the conventional bridging flocculants, and thus should have a sufficiently high molecular weight to give a bridging, as opposed to a coagulating, mechanism. Typically therefore the molecular weight is at least 5,000,000 and/or intrinsic viscosity is preferably at least 6dl/g.
  • the polymeric flocculant can be a natural or modified natural polymer but is generally a synthetic polymer formed from the monomers listed above. Since the coagulant is preferably cationic, the flocculant is preferably anionic, often sodium polyacrylate or a copolymer with acrylamide.
  • the separation process When the suspended material is solid (i.e., suspended or colloidally dispersed solids) , the separation process
  • SUBSTITUTE SHEET 16 preferably comprises a sedimentation process. It can consist solely of sedimentation but generally it involves a further dewatering step. Any such further dewatering step is generally conducted on the sediment obtained by the sedimentation. Such further processes include centrifugation and filtration, e.g., on a filter press or belt press.
  • One particularly preferred process of the invention involves applying the process to tailings from a coal washer or from an iron ore concentrator.
  • a coal washer or from an iron ore concentrator coal or iron ore is washed and the desired product (coal or iron ore) is separated by sedimentation or other appropriate separation technique to leave a liquor, termed tailings, that is a suspension of the waste products.
  • waste products often comprise clay.
  • Most of the solids may be suspended solids but some can be colloidally dispersed, as colourants.
  • Conventional processes involve adding a solution of coagulant polymer to the tailings as they flow along a duct towards a sedimentation tank, with flocculant solution generally being added immediately before the sedimentation tank .
  • the liquor resulting from the sedimentation generally still contains some suspended solids and can be coloured.
  • the process of the invention can result in a very clear, less coloured, liquor than is obtainable by conventional techniques, and yet avoids the need for a make-up unit or for the pumps or in-line dilution apparatus normally associated with the use of aqueous concentrates.
  • the preferred polymer for use in this technique is a homopolymer of diallyl dimethyl ammonium chloride (or occasionally a copolymer with up to 20% acrylamide) having intrinsic viscosity 0.5 to 3 (preferably 0.8 to 2.5) dl/g and that preferably fully dissolves within about one minute, preferably within about thirty seconds and most
  • SUBSTITUTE SHEET preferably within about fifteen seconds.
  • the polymer is preferably added in the form of beads which typically mainly have a size in the range 200 to lOOO ⁇ m.
  • a solution of flocculant e.g., sodium polyacrylate molecular weight above 5 million
  • the total time between adding the particles and introducing the suspension into the sedimentation tank is generally less than one minute, preferably less than about thirty seconds and most preferably is less than about fifteen seconds.
  • polymers of diallyl dimethyl ammonium chloride are particularly suitable for this process, other low molecular weight cationic polymers can be used, for instance polymers of cationic (meth) acrylates or cationic (meth) acrylamides, as discussed above.
  • aqueous suspension is a china clay effluent, for instance in the winning of such clays.
  • red mud washery liquors contaminated with colloidal humate can be decolourised by the addition of the chosen polymer in particulate form, instead of adding it in the conventional solution form as proposed in U.S. 4,578,255.
  • the invention is also of value in the treatment of organic suspensions and in the production of potable water. Less preferably, it can b used in cracking of oil-in-water emulsions.
  • suspension is a cellulosic suspension, for instance a white
  • Another important aspect of the invention includes the treatment of suspensions comprising sewage solids, for instance sewage sludge.
  • Another important aspect of the invention involves the removal of colouring matter and optionally suspended solids from potable water, typically prior to sedimentation or filtration through a sand bed.
  • the coagulatable material is, at all relevant times, a liquid and thus is not suspended solids nor colloidally dispersed solids.
  • the particulate coagulant may be added to an oil-in-water emulsion as a coagulant for cracking the emulsion.
  • the solids content of the suspension is generally below 10%, typically 0.02% to 8%, but another important aspect of the invention involves applying the process to suspensions having a higher solids content, typically 10 to 30%, for instance suspensions obtained by sedimentation in a previous separation process.
  • another process comprises dewatering a suspension (often after the addition of particulate coagulant as proposed in the invention) and then adding particulate polymer to the dewatered product and subjecting it to further dewatering after the polymer has dissolved, in accordance with the invention.
  • the optimum dosage of particulate coagulant polymer can be selected by routine experiments and is generally within or below conventional amounts of dissolved coagulant polymer. For instance it is often 0.1 to 20, frequently 0.5 to 5 mg/1 suspension.
  • a homopolymer is formed from diallyl dimethyl ammonium chloride by reverse phase bead polymerisation by the general technique shown in U.S. 4,506,062.
  • the beads have a particle size of 90% by weight between 200 and 800 ⁇ m and they have intrinsic viscosity of 1.4dl/g. Suitable beads are available from Allied Colloids Inc. under the trade name Percol 368.
  • Coal washings are subjected to froth flotation and the tailings from the flotation cells drop around 30 metres from the cells down a duct to the ground and to a pump by which they are pumped about 100 metres vertically upwards to a feed launder leading to a feed well at the inlet to a sedimentation (or thickener) tank.
  • a solution of anionic polymeric flocculant (copolymer of 60% acrylamide 40% sodium acrylate, IV about 16 dl/g) is added at the feed well, so as to promote settling in the tank.
  • the tailings have pH 7.4, around 7% solids material of which around 75% is below 100 mesh and is mainly clay.
  • the cationic polymer beads are screw fed into the tailings from the flotation cells as they leave the cells.
  • the polymer of example 1 is fed into a stream of coal tailings discharging from a primary settling pond to a secondary settling pond. Flow is by gravity down a pipe with a passage time of less than thirty seconds. The suspended solids of the overflow from the secondary settling pond is determined. With polymer dosages ranging 20 from 0.O025 to 0.0125 g/1, the suspended solids range from around 0.18% to 0.16% respectively.
  • the suspended solids range from 0.3% to 0.25% respectively. This again demonstrates the dramatic reduction in suspended solids obtainable by the use of the solid form of polymer in contrast to the solution form.
  • Example 3 the polymer is similar to example 1 except that it has higher molecular weight, intrinsic viscosity about 2dl/g.
  • a slurry of 1% kaolin in water containing lg/1 sodium chloride is prepared. 1 litre of the slurry is placed in
  • SUBSTITUTE SHEET a cylinder provided with a perforated steel plunger, depression of which causes mixing of the slurry.
  • the test polymer is added, at dosages ranging from 1 to 5 mg/1 and the slurry is subjected to 3, 6 or 9 plunges of the plunger.
  • the process is repeated using polymers of diallyl dimethyl ammonium chloride having, respectively, intrinsic viscosity 0.4, 0.9 and 2.0 dl/g.
  • the settlement rate and clarity is recorded. In every instance, the settlement rate is better, at a given number of plunges, for the solid polymer than the solution polymer and decreases with an increase in the number of plunges. In every instance the settlement rate of the polymer having IV 2 is better than the settlement rate for the polymer having IV 0.9 which, in turn, is better than the settlement rate for the polymer having IV 0.4dl/g.
  • the compaction deteriorates (increases) with an increase in the number of plunges and with decreasing IV.
  • the compaction is always better with the solid polymer than with the corresponding solution polymer.
  • a slurry is prepared of 1% china clay, 150mg/l sodium humate and 200g/l sodium hydroxide. 500ml samples of this slurry are stirred at I50rpm and dosed with various amounts of polymeric coagulant, either as solid or as aqueous
  • a slurry is made up as in Example 4 and then tested as in Example 4 using, as the coagulant polymer, powdered (or solution) sodium polyacrylate having molecular weight about 250,000. Turbidity and settlement rates are recorded. In every instance, the solid gives better settlement rate than the solution at 3 and 6 plunges, and although the trend continues to be true at higher numbers of plunges (i.e., continued turbulence, it is less distinct). For instance the solid grade polymer at lmg/1 gives settlement rates of 7.6, 5.7 and 4.5cm/min at 3, 6 and 9 plunges respectively, whereas the corresponding values when the polymer is added as a solution are 4.7, 4.3 and 4.0cm/min. There is no signficant difference in turbidity obtained using solid or solution polymers in this example.

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  • Cleaning Or Drying Semiconductors (AREA)

Abstract

Une suspension aqueuse d'une matière coagulable est coagulée par l'addition d'un coagulant polymère à la suspension, suivie de la séparation de la matière coagulée qui en résulte de la liqueur. La matière coagulable peut être présente dans la suspension aqueuse sous forme d'une suspension de solides ou sous forme de solides à dispersion colloïdale. La suspension peut se composer de schlamms de charbon ou d'autres suspensions aqueuses (généralement de minerais) . Le matériau polymère doit être composé d'un matériau polymère hautement ionique et de faible poids moléculaire. Il est ajouté à la suspension aqueuse sous forme de particules polymères d'une grosseur généralement supérieure à 30 νm et qui se dissoudront dans la suspension afin de coaguler la matière coagulable. Un floculant contre-ionique, de poids moléculaire élevé, est normalement ajouté par la suite afin de floculer la matière coagulée.
PCT/GB1991/000996 1990-06-29 1991-06-20 Purification d'une liqueur aqueuse WO1992000247A1 (fr)

Priority Applications (8)

Application Number Priority Date Filing Date Title
CA002076011A CA2076011C (fr) 1990-06-29 1991-06-20 Purification de liqueur aqueuse
DK91911284T DK0536194T4 (da) 1990-06-29 1991-06-20 Rensning af vandig væske
JP3510755A JPH06502112A (ja) 1990-06-29 1991-06-20 水性液の精製
DE69107456T DE69107456T3 (de) 1990-06-29 1991-06-20 Reinigung von wässrigen flüssigkeiten.
EP91911284A EP0536194B2 (fr) 1990-06-29 1991-06-20 Purification d'une liqueur aqueuse
AU79955/91A AU654135B2 (en) 1990-06-29 1991-06-20 Purification of aqueous liquor
NO924778A NO924778D0 (no) 1990-06-29 1992-12-10 Rensing av vandig vaeske
FI925860A FI925860A (fi) 1990-06-29 1992-12-23 Rening av vattenhaltiga vaetskor

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US546,435 1990-06-29
US07/546,435 US5178774A (en) 1990-06-29 1990-06-29 Purification of aqueous liquor

Publications (1)

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WO1992000247A1 true WO1992000247A1 (fr) 1992-01-09

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PCT/GB1991/000996 WO1992000247A1 (fr) 1990-06-29 1991-06-20 Purification d'une liqueur aqueuse

Country Status (13)

Country Link
US (1) US5178774A (fr)
EP (1) EP0536194B2 (fr)
JP (1) JPH06502112A (fr)
AT (1) ATE118462T1 (fr)
AU (1) AU654135B2 (fr)
CA (1) CA2076011C (fr)
DE (1) DE69107456T3 (fr)
DK (1) DK0536194T4 (fr)
ES (1) ES2068593T5 (fr)
FI (1) FI925860A (fr)
NO (1) NO924778D0 (fr)
WO (1) WO1992000247A1 (fr)
ZA (1) ZA915025B (fr)

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EP0643017A1 (fr) * 1992-08-18 1995-03-15 Nalco Chemical Company Coagulants polyélectrolytes hydrophobes pour concentrer des résidus de préparation du charbon
US9150442B2 (en) 2010-07-26 2015-10-06 Sortwell & Co. Method for dispersing and aggregating components of mineral slurries and high-molecular weight multivalent polymers for clay aggregation
US9540469B2 (en) 2010-07-26 2017-01-10 Basf Se Multivalent polymers for clay aggregation
EP2807120A4 (fr) * 2012-01-25 2015-08-05 Sortwell & Co Procédé de dispersion et d'agrégation de composants de suspensions minérales
US9487610B2 (en) 2012-01-25 2016-11-08 Basf Se Low molecular weight multivalent cation-containing acrylate polymers

Also Published As

Publication number Publication date
US5178774A (en) 1993-01-12
ES2068593T5 (es) 2002-04-16
NO924778L (no) 1992-12-10
DE69107456D1 (de) 1995-03-23
DE69107456T3 (de) 2002-05-02
FI925860A0 (fi) 1992-12-23
CA2076011A1 (fr) 1991-12-30
EP0536194A1 (fr) 1993-04-14
JPH06502112A (ja) 1994-03-10
EP0536194B2 (fr) 2001-11-14
ZA915025B (en) 1992-08-26
ATE118462T1 (de) 1995-03-15
DK0536194T3 (da) 1995-06-26
CA2076011C (fr) 2001-10-02
NO924778D0 (no) 1992-12-10
FI925860A (fi) 1992-12-23
DE69107456T2 (de) 1995-06-22
AU654135B2 (en) 1994-10-27
EP0536194B1 (fr) 1995-02-15
AU7995591A (en) 1992-01-23
DK0536194T4 (da) 2002-02-18
ES2068593T3 (es) 1995-04-16

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